Logging cable magnetic remark apparatus

Abstract

A magnetic mark on a cable is subject to loss of intensity. The present disclosure provides for remarking. It utilizes a detector which responds to passage of a magnetic mark on the cable. A coil for remarking is located at a specified and measured distance from the detector. Through the use of measuring wheels in contact with the cable providing data to a computer, the cable traverses from the detector to the marking coil, and a marker control circuit is timely operated to place a new mark on the cable. The new mark is placed coincident over the prior mark and has greater intensity to renew the magnetic marks on the cable.

What is claimed is: 
     
       1. An apparatus for remarking or reinforcing magnetic marks on a previously magnetically marked logging cable, comprising: (a) detector means for detecting passage of a previously marked magnetic mark on a logging cable wherein the cable is extended through said detector means and said detector means forms an output signal indicative of the passage of the previously marked magnetic mark therethrough;   (b) coil marking means spaced relative to the logging cable and sufficiently close thereto to form a magnetic mark on the cable, and wherein said coil marking means is located a predetermined specified distance from said detector means along the cable; and   (c) control means provided with measurements of cable travel, wherein said control means in also provided with an input signal from said detector means indicating passage of a previously marked magnetic mark on the cable, and said control means calculates cable traverse over said predetermined specified distance so that said coil marking means is controllably operated to place a magnetic remark on the cable coincident with the previously marked magnetic mark detected by said detector means.   
     
     
       2. The apparatus of claim 1 wherein said coil means comprises a solenoidal coil provided with current flow and forms magnetic flux which is coupled with the cable for marking the cable. 
     
     
       3. The apparatus of claim 1 wherein said control means has cable traverse measuring means connected thereto for determining cable travel over said predetermined specified distance. 
     
     
       4. The apparatus of claim 1 wherein said detector means and coil marking means are installed between a drum storing the cable thereon and a sheave positioned above the well borehole for directing the cable into the borehole. 
     
     
       5. The apparatus of claim 4 wherein said control means has cable traverse measuring means connected thereto for determining cable travel over said predetermined specified distance. 
     
     
       6. The apparatus of claim 5 wherein said cable traverse measuring means includes plural cable measuring wheels contacting the cable. 
     
     
       7. The apparatus of claim 6 including means for computing cable travel, said means for computing being responsive to an output signal from said cable measuring wheel. 
     
     
       8. A method of remarking a logging cable with magnetic marks which comprises the steps of: (a) deploying a logging cable between a drum and a sheave supporting that cable for movement therebetween;   (b) locating previously placed magnetic marks along the cable with a locating means;   (c) positioning a coil marking means adjacent to the cable at a known distance from said locating means for remarking on the cable and such that the cable's direction of motion carries a point on the cable past said coil marking means subsequent to passing said locating means;   (d) moving the cable between the sheave and drum to cause a located magnetic mark thereon to pass adjacent to the coil marking means;   (e) calculating cable traverse over said known distance; and   (f) operating the coil marking means solely in response to a signal from said locating means and said calculation to form a new magnetic mark coincident with the prior magnetic mark located on the cable.   
     
     
       9. The method of claim 8 including the step of supporting a weight on the cable to provide tension in the cable, and thereafter extending the cable to enable one or more marks on the cable to pass through said locating means for detection. 
     
     
       10. The method of claim 9 including the step of measuring cable movement by contacting a measuring wheel against the cable and forming a signal thereof. 
     
     
       11. The method of claim 10 including the step of locating a previously placed magnetic mark by positioning a mark detector adjacent to the cable to detect mark passage. 
     
     
       12. The method of claim 11 including the step of applying a pulse of current to the coil marking means to form a new mark on the cable. 
     
     
       13. The method of claim 12 including the step of controlling the current pulse relative to the cable by controlling the timing of the pulse in response to said signal generated by said locating means.